The present invention is a process for the preparation of silyl ketene acetals. The process comprises contacting a mixture comprising an organosilane having a silicon-bonded hydrogen (organohydrosilane) and a vinylic compound with RhCl(di-tert-butylsulfide).sub.2 as catalyst at a temperature within a range of about 20.degree. C. to 100.degree. C. The RhCl(di-tert-butylsulfide).sub.2 catalyst demonstrates higher activity than that typically described for rhodium catalysts, allowing for lower concentrations of catalyst and lower reaction temperatures to be used while maintaining high conversion to the desired silyl ketene acetals.
E. Yoshii et al.. Chem. Pharm. Bull. Jap. 22:2767-2769 (1974), describe the use of tris(triphenylphosphine)-chlororhodium as catalyst for the hydrosilation of several methyl 2-alkenoates with trialkysilanes. The process was run at 60.degree. C. to 100.degree. C. and a typical catalyst concentration was about 3.times.10.sup.-3 mole percent. Typical yields of the process for silyl ketene acetals were reported to be in the range of about 31 percent to 77 percent.
I. Ojima et al., J. Organometallic Chem. 111:43-60 (1976). also describe the use of tris(triphenylphosphine)chlororhodium as a catalyst for the hydrosilation of several methyl 2-alkenoates with trialkylsilanes. The times evaluated varied from one to 12 hours, the temperature from 40.degree. C. to 100.degree. C., and catalyst concentration from about 0.05 to 0.1 mole percent. Unlike Yoshii et al., Ojima et al. observed in addition to the silyl ketene acetals minor quantities of a 1,2-adduct.
J. Howe et al., J. Organometallic Chem. 208:401-406 (1981), describe two phosphine-rhodium(II) complexes found to be active catalyst for the hydrosilylation of a variety of organic substrates. The phosphine rhodium(II) complexes are bis(tris-o-tolylphosphine)dichlororhodium(II) and bis(tricyclohexylphosphine)dichlororhodium(II). The process described by Howe et al. was conducted at 100.degree. C. for eight hours, with catalyst concentrations in a range of about 0.4 to 0.6 mole percent.
Revis. EPO-219,322, Pub. Apr. 22, 1987, discloses a process for the manufacture of increasing yields of high-purity silyl ketene acetals, the process comprising the contacting of methacrylic acid or an ester of methacrylic acid with a hydrogen-containing silicon material in the presence of a catalyst comprising rhodium complexed with inorganic ligands. The preferred process parameters were reported to be a temperature between 40.degree. C. to 60.degree. C., a concentration of rhodium between 200 and 3000 ppm, and a reaction time greater than about one hour.